There are numerous marine vehicles for moving about underwater at shallow depths, making use of fins, pedal-driven propellers, etc. for human propulsion, or electric motors, combustion engines, etc. for motorized propulsion, or towing.
To move about underwater at greater depths, a watercraft is known from the prior art that is the object of patent application FR 2 951 134. This device and its variations have the following main features:                When the watercraft is submerged, the submerged structure is at least 1.5 meters underwater, requiring the use of breathing apparatus (SCUBA);        The speed when the watercraft is out of the water is limited to 12 knots;        The autonomy of the watercraft when underwater is limited because of the need for a breathing apparatus (SCUBA);        The construction costs;        The size of the craft.        
Also known from the prior art is a watercraft for exploring the seabed that is the object of patent application AU2007 234478. This document relates to a pleasure craft comprising a submersible support and a mechanism for raising and lowering the support. The mechanism as described is a rotating-arm system and the support can therefore be submerged in the water or raised out of the water by deployment of the rotating arms. This device, including the submersible support and mechanism, is incorporated into the vessel. Such a device makes the vessel quite cumbersome when in storage. In addition, such an exploration watercraft must be equipped with a suitable exploration device that is integrated with it. In addition, this watercraft is particularly suitable for diving with air tanks; this type of diving is not suitable for everyone and requires long preparation for the user.
There is therefore a need for systems for surface exploration with fins and snorkel, also called snorkeling, for inexperienced divers in particular.
The present invention is proposed to overcome some of the disadvantages of the prior art.